Institute for Science and International Security(ISIS) said that the latest satellite imageries obtained by itshows that the reactor building is relatively early in itsconstruction, but the footprint is that it is nearly of thesame size as that of the second and third Khushab reactors.

US and other reports had indicated that China andPakistan had recently concluded an agreement under whichBeijing would construct the fourth reactor at Khushab.

"A new construction staging and storage area can beseen south of the new construction. The new construction islocated several hundred meters south of second and thirdKhushab reactor compound," said a report authored by DavidAlbright and Paul Brannan.

The Washington Post said, "the new reactor, ifverified, would signal yet another step forward in Pakistan''sambitious effort to modernize and expand its nuclear arsenal."

Last month, the paper had reported that Pakistan''sstockpile was estimated to have grown more than 100 deployedweapons and to have surpassed that of India and even the UK.

Pakistan made its first nuclear reactor operational atthe Khushab site in 1998 and began construction of a secondreactor at the site after 2002.

In 2006, Pakistan began building a third reactor,adjacent to the second Khushab reactor.

"In first commercial satellite imagery from December2009, vapor could be seen rising from some of the secondreactor''s cooling tower fan blades, indicating that the secondreactor was at least at some stage of initial operation. Vaporcan again be seen rising from some of the second reactor''scooling towers in the January 15, 2011 imagery, though nonecan be seen yet over the third reactor''s cooling towers," ISISsaid.

"Another reactor just hammers the point that Pakistanis determined to make a lot of plutonium for nuclear weapons,frankly far more than they need or is healthy for the regionand the world," Albright was quoted as saying by The Post. PTILKJ ZH AKD